High-efficiency pulse compression with externally pumped intracavity Raman oscillators.

High-efficiency pulse compression has been obtained by using an externally pumped intracavity Raman oscillator. Through stimulated Raman scattering, the energy of a primary, long-pulse-duration omega(L) laser is downconverted and stored at the first Stokes frequency omega(1s) in a high-Q cavity containing the Raman medium. Then this electromagnetic energy is quickly extracted at the second Stokes frequency. This technique, which uses hydrogen gas as the Raman medium, permits a 25-nsec-duration ruby-laser pulse shortening by a factor of 12.5 with a near 50% quantum efficiency. Contrary to the case of intracavity Raman oscillators or amplifiers, this method can also be used with absorbing laser media.